Optical fiber technology is widely applied in communication, including telecommunication, data communication, cable television, and fiber-to-home applications. Optical fiber systems for some applications, including telecommunications and data communications, require high reliability and tolerance to harsh environments. The optical fiber collimator is a key component in an optical fiber system. It optically couples an optical fiber to an optical component. Optical fiber systems, in particular, optical fiber communication systems, employ a large quantity of optical fiber collimators because most optical fibers employed in these systems are terminated with optical fiber collimators. To improve reliability and tolerance to harsh environments, high reliability optical fiber systems employ ruggedized components, including ruggedized optical fiber collimators.
There are numerous prior art optical fiber collimator designs. In the past, the most important design goal for passive optical components was optimal optical transmission performance because the laser signal sources employed in an optical fiber communication system were expensive and not as reliable when compared to the passive components in the system, including optical fiber collimators. By optimizing the transmission performance of passive optical components in an optical communication system, the lowest power and therefore the least expensive and more reliable laser signal source can be employed in the system. FIGS. 1 and 2 illustrate representative prior art optical fiber collimator designs. Many of these prior art designs are optimized for optical transmission performance.
FIG. 1 shows a prior art optical fiber collimator design. Optical fiber 107 attaches to fiber ferrule 1. Fiber ferrule 1 and collimating lens 109 attach to housing 101. Housing 101 provides mechanical support to fiber ferrule 1 and collimating lens 109. In the fabrication process of this optical fiber collimator, optical fiber 107 is inserted into fiber ferrule 1 and secured to fiber ferrule 1. The end of optical fiber 107 and the end of fiber ferrule 1 are then polished to form optical fiber termination 108. To reduce reflection and improve optical transmission performance, the surface of optical fiber termination 108 is typically polished at an angle to the surface that is perpendicular to the axis of the fiber ferrule. The axis of the fiber ferrule is essentially the same as the optical axis of optical fiber 107 at optical fiber termination 108. Collimating lens 109 is placed at a distance from fiber termination 108. Similar to the surface at optical fiber termination 108, the surface of collimating lens 109 that is facing optical fiber termination 108 is polished at an angle to the surface that is perpendicular to the optical axis of collimating lens 109. This angle is introduced to the lens design to reduce reflection and to match the corresponding angle of optical fiber 107 at optical fiber termination 108. Fiber ferrule 1 and collimating lens 109 are then installed into housing 101. Although it is not necessary, either fiber ferrule or collimating lens 109 is secured to housing 101 to facilitate the alignment process. After that, the distance between optical fiber termination 108 and collimating lens 109 is adjusted, and either collimating lens 109 or fiber ferrule 1 is rotated about its optical axis for optimal optical transmission performance. After the alignment process, both fiber ferrule 1 and collimating lens 109 are secured to housing 101. Conventional fiber ferrule 1 is typically made from a capillary tube. One skilled in the art readily understands that there are numerous types of collimating lens or collimating lens system designs, optical fiber termination and termination methods, housing designs, and fiber ferrule designs commonly employed in optical fiber collimators.
FIG. 2 shows another prior art design. It is a variation of the design shown in FIG. 1. Compared to the design shown in FIG. 1, the design shown in FIG. 2 has a multi-piece housing that includes first housing 3 and second housing 4. Referring to FIG. 2, optical fiber 107 attaches to fiber ferrule 1 and collimating lens 109 attaches to second housing 4. Fiber ferrule 1 and second housing 4 attaches to first housing 3. Second housing 4 allows for the adjustment of the relative offset between the optical axes of optical fiber 107 at optical fiber termination 108 and collimating lens 109 to achieve the desirable optical transmission performance. As in the design shown in FIG. 1, conventional fiber ferrule 1 is typically made from a capillary tube. The material compatibility of capillary tube and optical fiber, however, limits the tolerance to harsh environments for these prior art designs.
In the past, laser sources were a primary limiting factor to optical fiber system reliability. With the advent of low cost high reliability laser sources for optical fiber systems, some of the passive components in an optical fiber system become primary limiting factors to system reliability. It is desirable to improve the reliability and ruggedness of passive components, including the optical fiber collimator, to improved system reliability. It is therefore an objective of this invention to provide a ruggedized optical fiber collimator.